Heat exchanger

ABSTRACT

A heat exchanger, especially for the cooling of gases emerging at high temperature and low pressure from reactors and the like in which the tube bundle is formed by a stack of tube arrays, each of which is constituted by a pair of corrugated plates having their corrugations in mutually facing and registering relationship. The pair of plates are stacked together in a housing permitting flow of the coolant between the arrays perpendicular and/or parallel to the tubes while the compartments are sealed at the ends of the arrays at which the tubes terminate by outwardly flared edges of the plates, which are of quartercircular cross section and are welded together along seams parallel to the plane of the tubes of the respective array. The tube sheets normally required in tube-bundle heat exchangers are thus constituted by the plates which also form the tubes.

United States Patent [72] Inventor Gama! ElDln Nasser 2,973,749 3/1961 Huet 165/IOS Planegg, Germany 3,306.351 2/1967 Vollhardt 165/140 [2]] Appl. No. 773,082 3.346.042 10/1967 Seehausen 165/ I44 [22] Filed I968 Primary Examiner-Charles Sukalo Patented Oct- 5, y Ka F. Ross [73] Assignee Linde Alttlengesellsehaft Wlesbaden, Germany [32] Priority Nov. 3, 1967 [33] Germ-y ABSTRACT: A heat exchanger, especially for the cooling of [31] P16 01 215.0

gases emerging at high temperature and low pressure from reactors and the like in which the tube bundle is formed by a [54] HEAT EXCHANGE]; stack of tube arrays, each of which is constituted by a pair of 17 cm I Dnwlng m corrugated plates having their corrugations in mutually facing and registering relationship. The pair of plates are stacked [52] 0.8. CI 165/158, together in a housing permitting flow of the coolam between 65/166 the arra s er endicular and/or parallel to the tubes while the s in C1 rzsrsoz y p p l] t. compartments a sealed 8 the ends of the arrays at which tI: 0' tubes erminate outwardly flared edges of the p l 18 are of quarter-circular cross section and are welded together along seams parallel to the plane of the tubes of the respective [56] References Cited arrayv The tube sheets normally required in tube-bundle heat UNn-ED STATES PATENTS exchangers are thus constituted by the plates which also form 2,526,157 10/1950 Ramew 165/166 the tubes.

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BY 001A R Attorney HEAT EXCHANGER My present invention relates to a heat exchanger and, more particularly, to an apparatus for the cooling of gases at elevated temperatures and low pressures, especially the fw sion-fragment-containing gases of nuclear reactors, hot waste gases for instance from furnaces, and hot effluent gases of chemical reactors, and the like with a cooling medium of a high pressure.

It has already been proposed to provide heat-exchange systems for the cooling of hot-gas streams which traverse a multiplicity of generally rectilinear or straight tubes held in place by a pair of tube sheets at the ends of the tube bundle, while a cooling fluid, which may be of higher pressure, flows between the tubes of the bundle. ln such systems, it is a common practice to provide means for reinforcing the tube sheets against the stresses generated by the elevated-pressure cooling medium.

Tube-bundle heat exchangers having tube sheets at the gasentry side of the device have the substantial disadvantage that a relatively large temperature differential exists across the tube sheet which, at one side, is exposed to the high-temperature gas and, at its other side, is exposed to the low temperature and high pressure cooling medium.

Additionally, the tube sheet is subjected to a substantial pressure differential equal to the difference between the hotgas pressure on the entry side and the coolant pressure on the opposite side of the tube sheet. In order to accommodate the thermal and pressure stresses, it has been found to be necessary to use relatively thin-walled tube sheets (rather than massive or thick tube sheets) and to obtain the necessary mechanical stiffness by the use of reinforcing webs or rods constituting a lattice work or the like. This arrangement is both expensive and unsatisfactory at best since the cooling efficiency is relatively low and the use of the system is characterized by overheating and accelerated corrosion of the heatexchange walls, especially when a condensable or condensatecontaining medium is used. Attempts to avoid this problem by passing the high-temperature gas through the chamber surrounding the tube bundle and the cooling medium through the tubes thereof have hitherto not been fully satisfactory either. Such systems involve high-pressure drops in the tube bundle, decreased heat-exchange efficiency and elevated pressure drops in the heat exchange medium.

It is, therefore, the principal object of the present invention to provide an improved heat exchanger for the indirect heat exchange across a heat-transfer wall wherein the aforementioned disadvantages can be avoided and heat-exchange efficiency increased.

Another object of this invention is the provision of a tubebundle heat exchanger adapted to be traversed by low-pressure high-temperature and which is of simple and inexpensive construction, but has greater heat-exchange efficiency than prior art systems and a very little pressure drop.

Yet another object of the instant invention is the provision of an improved heat exchanger for the cooling of high-temperature gases at low pressure and especially gases of the type described above with a cooling medium of a high pressure.

These objects and others which will become apparent hereinafter can be attained, in accordance with the present invention, in a tube-bundle heat exchanger formed with a pair of tube plates lying in planes parallel to the array of mutually parallel tubes to be formed therebetween and having on their confronting sides a plurality of spaced-apart parallel concavities or corrugations which mutually register to constitute the respective tubes between them.

The relatively thin-walled plates are preferably formed with the respective concavities by deformation of the plates in the manner of corrugations with each concavity extending over an arc segment of about I80 and the concavities being separated by webs which lie in a diametral plane of the tubes of the array and are generally planar, so as to be coextensive with the corresponding webs of the confronting plate, and form reinforcing ribs between each pair of tubes of the particular array. Consequently, it can be said that each tube of the heat exchanger in accordance with the present invention is defined between a pair of such plates which are in approximate mirror symmetry about a plane of symmetry extending through the axes of all of the tubes of a particular planar array and through the abutting faces of the flat rectangular webs between each pair of tubes of the array.

The tubular members themselves are constituted by semicylindrical corrugation troughs which, as has been noted, register with corresponding troughs of the oppositely facing plate. The plates, according to this invention, are generally rectangular in plan view but are formed at their small sides or ends with outwardly flared or bent quarter-round flanges or marginal portions which are welded to the outwardly turned corresponding flanges at neighboring plates of adjacent arrays so that the interconnected flanges together from endwalls or "bottoms" of the chambers between the tubes constituted by the pairs of mutually facing registering corrugations in a construction generally similar to that of a unitary tube sheet. Furthermore, the longitudinal edges of the plates of each array, which run parallel to the corrugations and thus of the tubes constituted thereby, are welded together.

According to a further feature of this invention, the tubes of each array defined between each pair of such plates formed with corrugations are oifset or staggered approximately by the diameter of the tubes perpendicular to the tubes in the adjacent planes of the respective arrays. When each pair of plates is formed with an array of semicylindrical corrugations as indicated earlier, the plates can be constituted as unit elements reversed with respect to one another and of identical form whereby the plate may be welded together in mirror symmetry. A stack of similar plates may thus be joined to form the tube bundle, with the plates being mass produced at relatively low cost.

According to another aspect of this invention, each of the plates is of a length slightly more than twice the length of the tube array and is bent at one end of the rectangle to form a pair of plate portions whose corrugations open in opposite directions and thus constitute right-hand tube halves of one planar tube array and left-hand tube halves of the next array. The width of this double-length plate corresponds to the height of the tube arrays. At the bent end and at the opposite end of the arrays, the rounded outwardly curved flanges are provided for welding contiguously to the adjoining sets of plate portions into an integral tube bundle. Advantageously, the corrugations in the tube portions of the double-length plates are so formed as to be offset from one another by approximately half of the center-to-center distance between the pairs of semicylindrical corrugations.

According to another feature of this invention, the end edges of the bars of the plates are provided with graduated or transition members of flanges, which may also be described as leveling flanges, adapted to affix the tube bundle to the heat exchanger housing. To this end, the housing may comprise an elongated casing which surrounds the body of the tube bundle and is provided with radial inlet and outlet fittings to which cooling liquid is supplied and for the removal of the rest of the cooling liquid and vapors formed in the coolant compartment. Advantageously, the housing also comprises a pair of hood members in the form of angular flanges to which the leveling flanges of the plates are welded.

Preferably, the ends of the plates proximal to these flange rings are formed with corrugations or plated portions designed to accommodate thermal expansion or contraction stresses at the hot-gas side of the tube bundle. The space between the tube arrays at each end of the tube bundle is thus defined between sets of covers and walls constituted by the quartercircular outwardly flared edges of the plates which thus are welded together along the seams transverse to the tubes but parallel to the common axial plane of each tube array. The transition or leveling flanges or members are provided to ac commodate the outer boundaries of the tube bundle to the flanges of the housing which may be bolted to the casing sandwiched between them.

The flanges of the housing are provided, in accordance with another feature of this invention with inlet and outlet hoods for the introduction of the hot gas to be cooled and for the effluent gases. respectively.

Because of the seams connecting the outwardly flared edges of the narrow ends of the adjacent tube array only the tubes defined between each pair of plates communicate with the hood which this form manifolds at the opposite longitudinal ends of the tube bundle The coolant passes through the tube bundle in spma between the tube arrays enclosed by the seamed outwardly turned edges.

In accordance with another concept included in the present invention, the edge portion of the plates which form the tubes and are affixed to the housing wall transversely of the direction in which the tubes run and laterally of the manifold ends of the asembly are relatively wide to space the tubes closest to the housing wall at a substantial distance therefrom, greater than the spacing between the tubes, thereby accommodating a temperature gradient corresponding to the temperature difference between the tube and the coolant or the coolant-enclosure housing. Thus I am able to destress the welded teams at which the tube bundle is fixed to the housing flanges, the thermal stresses resulting from the temperature differences being taken up by the relatively wide sheet-metal strips along the respective plates.

It will be evident that the tube bundle of the present invention eliminates the need for tube sheets at the opposite ends of the heat exchanger, since the closure of the coolant changer is accomplished by the ends of the same plates which produce the tubes. The tubes and end walls thus have practically the same wall thickness thereby eliminating temperatures differential stresses between tubes and tube sheets. The invention also provides that the outwardly graded edges of the plate at both ends of the tube bundle may have reinforcing webs or ribs which are set inwardly from the seams by which these edges are joined to the housing and run transversely to the tube plates but parallel to the aforementioned outward edges, thereby stiffening the latter. Best result are obtained when the corrugations are circular so that they are in effect semicylindrical.

Still another feature of this invention resides in the provision of the housing structure such that the inlet for the coolant liquid is located at the bottom of the unit while the outlet means extends upwardly therefrom and communicates above the housing with a separate drum in which condensate is precipitated. This drum is connected via a conduit with one or both of the inlet fittings, in a return path for the accumulated liquid. In one particular advantageous arrangement of the device, the housing is formed at its lower side with a plurality of inlet fittings for liquid coolant which can be connected separately or collectively to the precipitating drum.

When the aforementioned inlet and outlet hood are provided, I prefer to have them terminate at a short distance from the tube bundle and, in addition. to provide a gap between the tube bundle and the surrounding walls of the housing; bafiles or perforated plate structures span the gaps between the tube bundle and the wall to restrict the flow cross section of the hot gas mixture by passing the tube bundle at these gaps. The horizontal arrangement of the gas cooler has been found to be substantially desirable for the cooling of reactor gases and especially for the removal of ethylene from ethylene furnaces in which ethane or higher hydrocarbons (for instance naphtha) serves as the raw material. In such reactor gas coolers the heat exchanger can be mounted directly at the outlet of the furnace and used as a precooler in order to minimize the residence time of the hot gases. which must be as short as possible whereupon a further heat exchange unit, e.g., vertical coolers may be supplied with the effluent gases.

It is also an important advantage that a sudden acceleration of the hot gases entering the tubes does not occur, which occurrence would effect an undesired reaction.

Another advantage of the present invention resides in the fact that the flow cross section of the gas tubes of this invention can be varied to accommodate reduced flow rate and prevent a reduced cooling with decreasing flow velocity or to minimize pressure drop. The control of the flow cross section may make use of the pressure within the coolant chamber which can vary the effective cross section of the tube by com pressing the corrugations for allowing them to expand. Best results are obtained for this purpose when the plates are formed with curved semitubular corrugations.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. I is a vertical axial cross-sectional view through a horizontally disposed gas cooler according to the invention, the view corresponding to a section along the line l-l of FIG. 2;

FIG. 2 is a cross-sectional view of a portion of the heat exchanger taken generally along the line II-II of FIG. 1;

FIG. 3 is a detail view of the weld seam along the edge of one of the plates of the tube assembly corresponding substantially to a section along the line III-III of FIG. 4;

FIG. 4 is a fragmentary cross-sectional view drawn to the same scale as FIG. 3 and corresponding to a section along the line IV-IV of FIG. 3;

FIG. 5 is a detail view drawn to the scale of FIG. 3 and 4 and constituting a section along the lines V--V of FIG. 2 and of FIG. 4;

FIG. 6 is an end view of a plate assembly for forming a pair of tube arrays according to the present invention prior to the assembly of the arrays into a unit;

FIG. 7 is an end view corresponding generally to FIG. 6 but illustrating an embodiment of the present invention wherein each plate has a pair of plate portions folded into mutually parallel relationship so that the semicylindrical corrugations on each plate section open in opposite directions. the plate sections being shown prior to joining them into a tube unit;

FIG. 8 is a vertical cross section generally along the axis of an upright heat exchanger is accordance with the present in vention and corresponding substantially to a section along the line VIII-VIII of FIG. 9;

FIG. 9 is a horizontal cross section generally along the line IX-IX of FIG. 8 and through the vertical gas-cooling heat exchanger thereof; and

FIG. 10 is a diagram illustrating the application of this invention to reactor gas cooling.

As can be seen generally from FIGS. 1 and 2, a horizontally disposed gas cooler in accordance with the present invention comprises a tube bundle TB having ends walls EW and EW' which can be considered to replace the usual bottoms" or tube sheets at the opposite ends of a conventional tube-bundle heat exchanger in which these plates are perforated and receive the tubes which span the sheets.

From FIG. 2, it will be seen that the tube bundles of the present invention comprise mutually parallel pair of plate 1 and 1' constituting the rightand left-hand plates of each tube array TA. The tube arrays consist, therefore, of horizontally running cylindrical tubes T,, T,, T,, etc.. in mutually parallel vertically spaced relationship such that the distance D between the centers C of these tubes is greater than the diameter :1 thereof, ensuring a spacing S between the tubes. The spacing S is fonned by a pair of webs W and W which are coextensive with each other and abut along a flat surface defined by the vertical median or axial plane P through the centerline C of the array. The webs W and W may have a width w which is equal more or less to the radius (i=d/2) of the tubes T. The plates 1 and 1' shown in FIG. 2 are representative of sets of plates 2. 2'; 3, 3'; 4, 4'; and 5,5 which differ from one another as will be pointed out hereinafter. Each set of plates, however, may be considered to have a plane of symmetry at P and to be mirror symmetrical with respect to this plane. Consequently, the semicylindrical corrugations SC and SC of the plates 1, I, etc., are vertically and horizontally coextensive and register with one another to form the tubes 'I,T;,, etc. as noted earlier.

Thus, FIGS. 1 and 2 show a tube bundle for a heat exchanger in which the vertical plates 1, l to 5, 5' are formed with mutually facing arrays of vertically spaced half-tube or semicylindrical corrugations which define the tubes between them. The alternate tube arrays, e.g., Ta and TA TA, and TA,, etc., have the tubes offset from one another by a distance A ranging from r approximately the diameter d of the tubes.

The tube bundle shown in FIG. 2 thus consists of five identical sets of plates l, 1', four identical sets of plates 2, 2', and single pairs of plates 3, 3', 4, 4' and 5, 5'. The plates 1 and 1', 2 and 2', 3 and 3', 4 and 4' and 5 and 5' ofthe pairs each may be identical to the other and merely inverted to stand in minor symmetrical relationship. Since the entire tube bundle can be composed of such plates, it is evident that only five different types of plates need be made for heat exchangers of this character regardless of the capacity of the heat exchanger, provided the tube diameters, spacing and tube number for each array are to remain constant. in other words the plates assigned to each array can be formed with semicylindrical corrugations and can be completely identical but one plate is rotated through 180 in its plate and reversed back to front to bring it into juxtaposition with the nonrotated plate as shown in FIG. 2.

As will be apparent from FIG. 2, the plates 1, 2, 3, 4 and 5 (unprimed reference numerals) have relatively wide marginal portions M M,, etc., turned upwardly while the corresponding primed numeral plates (1' to 5') have narrow marginal portions M,', M,, turned upwardly so that welds 6' to are provided between the marginal portions and to seal the edges of the paired plates; insert plates 1,, may be welded between the marginal portions and the longitudinal walls of the tube bundle. Thus, the foreshortened sides are sealed to the nonforeshortened sides by weld seams formed at 6, 6'; 7, 7'; 8, 8'; 9, 9'; and l0, 10', thereby preventing escape of gas from or entry of liquid into the respective arrays; the seams are respectively located such that the first of each pair is positioned below the lowest tube T,, T, etc., of each array while the other is disposed above the uppermost tube of the array on the opposite side of the respective median planes.

The vertical end edges of the plates 1, l; 2, 2'; 3, 3'; 4, 4; and 5, 5' are bent away from one another into approximately quarter-circle configurations or profiles so that each two arrays of tubes Ta can be welded at both ends at their bent sheet metal edges to form an end wall EW or SW. The upper end ll and the lower end ll of the sheet metal edges of each plate are stepped downwardly to form transition pieces and are reinforced with webs l2 and 12', respectively, for additional stiffening (see FIGS. 3-5). The corresponding outer edges 13 of the plates 1, l; ...5, 5', which lie in common vertical planes, are welded to welding shoulders 14 which extend inwardly from the housing or shell flanges 15.

The housing of the heat exchanger of FIGS. 1-5 comprises a cylindrical shell 16 which is formed at diametrically opposite locations with a pair of inlet pipe fittings 17 at one side and a pair of outlet pipe fittings is of the other side. A cooling liquid is introduced at elevated pressure at 17 from below and is withdrawn at 18 as a mixture of the liquid with vapor generated in heat exchange with the gas traversing the tubes of the arrays TA, TA,, The outlets 18 lead to a condensate collecting chamber above the shell 16 from which liquid coolant is returned to the inlet side at 17. The fittings l7 and 18 are welded to the shell 16 at seams l7 and 18', respectively.

At the opposite ends of the shell 16, the latter (which is composed of relatively thick or massive cast metal) is butt welded at annular seams 16 to the inwardly converging bosses of the connecting flanges 15. The latter have inwardly projecting shoulders l4 to which the outer edges 13 are welded as has been indicated earlier. To the flanges I5, I have bolted support rings 22 at each end of the housing, the support ring forming a pair of hoods with respective conical bodies 21 which are welded to the respective support ring at circular seams 21'. The annular bodies 21 are also welded at 21" to the funnel-shaped inlet cap 200 and to the outlet funnel 206, both of which are formed with cylindrical hood portions and 200, respectively. The diameter and cross section of the members 20 and 20c is such that it corresponds substantially to a vertical section through the tube bundle. The hot reactor gas flows through the heat exchanger from the inlet 1, N and emerges from the outlet OUT after traversing the tubes T,, T,, of the tube bundle. The members 20 and 200 are spaced by a distance a (FIG. 1) from the end walls EW and EW' of the tube bundle TB. THe rings 22 are attached to the flanges 15 by bolts 22'. The space 23 between the rings 22 and the members 20 and 20c can be packed with a thermally insulating material such as glass, wool, batts or any other thermal insulation.

The vertical outer edges of the plate 5', which are rounded in domelike configuration as shown at 50 in F IG. 2 are welded to a further plate 5" whose edges are likewise rounded or bent into a curved configuration and which is, in turn, welded to the shoulder 14 of the respective flange 15 described above. The plates 5" on either side of the tube bundle serve to relieve stress on the flanges 15 which close the coolant medium chamber and thus must withstand the relatively high pressure of the coolant. Along the upper edges of the plates 5' on each side of the tube bundle, I provide guide plates 24 which run horizontally, are welded to the plates 5" and are provided with perforations 24 to restrict an upward stream of liquid/vapor coolant mixture from passing around the sides of the tube bundle and thereby confining the coolant to movement in the direction of arrows C in FIG. 2.

FIGS. 3-5 show the details of the comer and edge junctions of the plates 1, l... as has already been discussed. It can be seen here, however, that in addition to the weld seams 6', 7', transverse weld seams 6" are provided to seal the coolant chamber. The flush end wall 11, its stifi'ening webs l2 and the weld seam 13 can also be seen here. It should be noted that transverse corrugations are provided (e.g., at 25 in FIGS. 4 and 5) along the vertical edges of the plate to accommodate thermal expansion and contraction of the assembly.

FIGS. 3-5 and 5A show that each tube is constituted by a pair of corrugations 2a, 2a (FIG. 5) whose longitudinal sides abut at 2c while the edges of the plates 2 and 2' are turned of flared outwardly at 24 and 2d respectively. As illustrated in FIG. 5, the edge 2d is welded at 2e to the oppositely turned edge I of an adjoining plate, thereby defining a closed compartment K between the two arrays of plates through which the coolant liquid can rise from the inlet fittings 17 to the outlet fittings 18 in a direction perpendicular to the plane of the paper as shown in FIG. 5. These scams 2: are represented as well in FIG. 5A and can be seen to run vertically parallel the medium plane P of each array. THe portions of the plates at the upper and lower sides of the vertical ends (corresponding to the seam side 2e) are secured at l3 to the rings 15 via the shoulders 14 with the aid of transition or leveling edges ll which accommodate the inner rim of the shoulder l4 FIG. I) to the undulating end walls EW, EW' of the tube bundle T8. The plates or corrugations 25 formed in the relatively wide edge portions which are either unitary with the plate or constituted by the inserts l and l, etc.

In FIG. 6, l have shown two arrays of structural elements or plates which are represented at l, 1' and 2, 2 to illustrate in greater detail the assembly of this invention. The plates 1 and l are of identical construction and have been reversed relatively and rotated with respect to one another through l in the plane of the rotated plate to bring the corrugations into registry and form the tubes T. Similarly. the plates 2 and 2' are identical to one another. The weld seams 6 and 6, and 7, 7', alternately above the upper and below the lower tube of each array and on opposite sides of the median plane P, secure the plates together in the event insert plates l, etc., are not used. The welds 6, 6' constitute the longitudinal seams of the tube arrays. It may be pointed out that the transverse weld seams 6" are extended across the plates below the transition piece ll to seal the cooling medium compartment K (see FIG. 5

The tube arrays shown in FIG. 6 are welded together along their outwardly flared quarter-cylindrical vertical edges 26 seen from within the compartment K between the tube arrays in FIG. 6.

As is apparent from FIG. 7, the assembly is made of plates 101, 102 each comprising a pair of plate portions 1010, 101b and 1020, 1112b formed with respective arrays of semicylindrical corrugations 101a, 1011), and 1020', 1026', respectively, the corrugations being offset from one side of the plate assembly to the other in the vertical direction by approximately the diameter of the tube to be formed between the corrugations. Thus the plate 102 has an array of corrugations 102a and "DH in staggered relationship, the corrugations 102a registen'ng with the corrugations of the adjoining plate. The portions 101a and llllb and the portions 102a and 10211 of the plates are formed by folding the stamped bodies 101 and 102 about their bight portions Nile and 10% and providing them with weld seams at the vertical edges opposite the bight 101c, 102c not shown in FIG. 7. The two sets of plates can be welded together along seams at 106 and 107 alternately on opposite sides of the median plane when the two plates are brought into contact with one another. It will be apparent that this assembly provides one longitudinal end of the tube bundle with seamless junctions between the plate portions of each plate while the opposite longitudinal end provides seams running in the vertical direction as shown with respect to the seams 2c in FIGS. 2 and 5. I prefer to introduce the reactor gas which is cooled by the present heat exchanger at the nonseamed side of the tube bundle.

In FIGS. 8 and 9, I show a vertical heat exchanger for the cooling of reactor gas, e.g., as a final gas cooler connected to a precooler formed, for example, by the horizontal cooler of FIGS. l-7 This cooler is formed with a cylindrical housing 216 to which a pair of outwardly flared bells 216 and 216 are welded at seams 216a and 216a". The bells are closed by the flange ring 215 at weld seams 215' while shoulders 214 of the flanges 215 are welded to the tube bundle TB which may have the construction shown in FIGS. 1-6, the reference numerals used in describing the tube bundle being equally applicable here. In this heat exchanger, however, the tube bundle comprises three pairs of plates 1, 1, two pairs of plates 2, 2', and two plates each at 3, 3; 4, 4'; and 5, 5' in analogy to FIG. 2. At the latter semitubular corrugated plate 5', a planar bridging plate 5" is provided to relieve stress at the flanges 215. The coolant enters from below at two diametrically opposite locations via fittings 217 and is distributed through the channels K between the arrays of tubes. The liquid/vapor mixture formed by heating of the coolant passes upwardly and exits through a plurality of radially outwardly extending fittings 218.

in FIG. 10, l have shown a heat-exchange assembly in which an ethylene furnace EF feeds a horizontal precooling heat exchanger of the type described in connection with FIGS. 1-7 and indicated at GC,. A precipitator Cl, above this cooler collects the coolant vapor mixture and returns the coolant to one of the inlet fittings of the gas cooler GC,. From the latter, the reactor gas passes upwardly through a second cooling stage represented by the embodiment shown in FIGS. 8 and 9 and which also is provided with a precipitator CP, which returns liquid coolant to the inlets of the second gas-cooling stage GC, The cool gas emerges at 0 and higher hydrocarbons as ethane may be fed to the furnace EF as represented at R.

The improvement defined and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

1 claim:

1. A heat exchanger, especially for heat exchange between a liquid coolant evaporating at high pressure and a hot gas at low pressure, said heat exchanger comprising a stack of arrays of mutually parallel transversely spaced coplanar tubes, each array being defined by the oppositely facing concavities of respective corrugations formed in a pair of juxtaposed plates of uniform cross-sectional thickness whereby the corrugations of each plate form respective tube halves, the edges of the plate pairs parallel to the longitudinal dimensions of the corrugations being welded together, said arrays of tubes collectively constituting a tube bundle open at the ends of said tubes, the plates of each of said arrays having outwardly flared smoothly curved edges welded to the corresponding edges of a plate of an adjacent array in a weld seam of substantially said thickness at least at one side of the tube bundle at which said tubes open, thereby forming seams closing respective compartments parallel to said arrays and between them, said compartments having uniform thickness smoothly curved walls at the sides of the tube bundle; first means for passing a first evaporating high-pressure heat exchange fluid through said compartments in a direction transverse to sad tubes; and second means for passing a low-pressure hot gas as the second heat exchange fluid through said tubes from one end of said tube bundle to the other end thereof.

2. The heat exchanger defined in claim 3 wherein the juxtaposed plates of each of said pairs are substantially identical to the other plates of said respective pair but reversed by rotation through lin its plane about an axis transverse thereto.

3. The heat exchanger defined in claim 1 wherein said outwardly flared edges are of quarter-circular cross section and are butt welded whereby said respective compartments are closed by said seams and provided thereby with semicircular walls, said corrugations being of semicircular profile.

4. The heat exchanger defined in claim 3 wherein the juxtaposed plates of at least one of said pairs are formed by plate portions of a single elongated body folded at the end of the array opposite the respective said seam whereby the corrugations of the portions of said body open away from one another.

5. The heat exchanger defined in claim 4 wherein the tubes of the adjacent arrays are staggered transversely in the respective planes.

6. The heat exchanger defined in claim 5, further comprising a housing surrounding said tube bundle and formed with a pair of end flanges respectively carrying an inlet and an outlet duct constituting said second means, said ducts communicating with said tubes.

7. The heat exchanger defined in claim 6 wherein said plates have end edges welded to said flanges and graded toward the latter, said end edges sealing said compartments and being formed with pleats accommodating thermal stress at the junction of said plates with said flanges.

8. The heat exchanger defined in claim 6, further compris ing reinforcing webs extending transversely to said plates and parallel to said tubes and welded between plates joined by a respective said seam to stiffen the respective wall of the compartment between the plates.

9. The heat exchanger defined in claim 6 wherein the cross section of said inlet duct corresponds substantially to the cross section of said tube bundle at said one side thereof but is spaced from said tube bundle.

10. The heat exchanger defined in claim 9 wherein each of said flanges defines an annular space with the respective duct, said heat exchanger further comprising a mass of thermal insulation filling said space.

11. The heat exchanger defined in claim 6 wherein said housing includes a shell and said first means includes at least one inlet communicating with said compartments and formed in the bottom of said shell and at least one outlet communicating with said compartment on the opposite side of said tube bundle from said inlet and formed in an upper portion of said shell.

12. The heat exchanger defined in claim 11 wherein said first fluid is a vaporizable liquid and said outlet is connected to a precipitator adapted to collect liquid from a vapor/liquid mixture emerging from said outlet, said precipitator being provided with conduit means connecting said precipitator with said inlet for returning coolant liquid to the latter.

13. The heat exchanger defined in claim 12 wherein said precipitator is a drum overlying said shell.

16. The heat exchanger defined in claim 3, further comprising means for selectively varying the flow cross section of said tubes.

17. The heat exchanger defined in claim 3 wherein one of the plates of each pair is cut away in a direction transverse to the respective corrugations and is welded to the other plate along a weld seam sealing said tubes from said compartments. 

1. A heat exchanger, especially for heat exchange between a liquid coolant evaporating at high pressure and a hot gas at low pressure, said heat exchanger comprising a stack of arrays of mutually parallel transversely spaced coplanar tubes, each array being defined by the oppositely facing concavities of respective corrugations formed in a pair of juxtaposed plates of uniform cross-sectional thickness whereby the corrugations of each plate form respective tube halves, the edges of the plate pairs parallel to the longitudinal dimensions of the corrugations being welded together, said arrays of tubes collectively constituting a tube bundle open at the ends of said tubes, the plates of each of said arrays having outwardly flared smoothly curved edges welded to the corresponding edges of a plate of an adjacent array in a weld seam of substantially said thickness at least at one side of the tube bundle at which said tubes open, thereby forming seams closing respective compartments parallel to said arrays and between them, said compartments having uniform thickness smoothly curved walls at the sides of the tube bundle; first means for passing a first evaporating high-pressure heat exchange fluid through said compartments in a direction transverse to sad tubes; and second means for passing a low-pressure hot gas as the second heat exchange fluid through said tubes from one end of said tube bundle to the other end thereof.
 2. The heat exchanger defined in claim 3 wherein the juxtaposed plates of each of said pairs are substantially identical to the other plates of said respective pair but reversed by rotation through 180*in its plane about an axis transverse thereto.
 3. The heat exchanger defined in claim 1 wherein said outwardly flared edges are of quarter-circular cross section and are butt welded whereby said respective compartments are closed by said seams and provided thereby with semicircular walls, said corrugations being of semicircular profile.
 4. The heat exchanger defined in claim 3 wherein the juxtaposed plates of at least one of said pairs are formed by plate portions of a single elongated body folded at the end of the array opposite the respective said seam whereby the corrugations of the portions of said body open away from one another.
 5. The heat exchanger defined in claim 4 wherein the tubes of the adjacent arrays are staggered transversely in the respective planes.
 6. The heat exchanger defined in claim 5, further comprising a housing surrounding said tube bundle and formed with a pair of end flanges respectively carrying an inlet and an outlet duct constituting said second means, said ducts communicating with said tubes.
 7. The heat exchanger defined in claim 6 wherein said plates have end edges welded to said flanges and graded toward the latter, said end edges sealing said compartments and being formed with pleats accommodating thermal stress at the junction of said plates with said flanges.
 8. The heat exchanger defined in claim 6, further comprising reinforcing webs extending transversely to said plates and parallel to said tubes and welded between plates joined by a respective said seam to stiffen the respective wall of the compartment between the plates.
 9. The heat exchanger defined in claim 6 wherein the cross section of said inlet duct corresponds substantially to the cross section of said tube bundle at said one side thereof but is spaced from said tube bundle.
 10. The heat exchanger defined in claim 9 wherein each of said flanges defines an annular space with the respective duct, said heat exchanger further comprising a mass of thermal insulation filling said space.
 11. The heat exchanger defined in claim 6 wherein said housing includes a shell and said first means includes at least one inlet communicating with said compartments and formed in the bottom of said shell and at least one outlet communicating with said compartment on the opposite side of said tube bundle from said inlet and formed In an upper portion of said shell.
 12. The heat exchanger defined in claim 11 wherein said first fluid is a vaporizable liquid and said outlet is connected to a precipitator adapted to collect liquid from a vapor/liquid mixture emerging from said outlet, said precipitator being provided with conduit means connecting said precipitator with said inlet for returning coolant liquid to the latter.
 13. The heat exchanger defined in claim 12 wherein said precipitator is a drum overlying said shell.
 14. The heat exchanger defined in claim 3 wherein said second means is connected directly to the output of a gas reactor furnace for the formation of olefins.
 15. The heat exchanger defined in claim 14 wherein said heat exchanger constitutes a precooler for the gases emerging from said furnace, further comprising a vertical cooler connected to said second means downstream of said tube bundle for further cooling of the reactor gases.
 16. The heat exchanger defined in claim 3, further comprising means for selectively varying the flow cross section of said tubes.
 17. The heat exchanger defined in claim 3 wherein one of the plates of each pair is cut away in a direction transverse to the respective corrugations and is welded to the other plate along a weld seam sealing said tubes from said compartments. 